new chiappa M4-22 upper on new plum crazy lower will not fire

pinned it together, round chambed act's like firing pin not hitting, no marks on the round, pulled bcg out wiped off & oiled, put paint on firing pin, put back together went click. pulled apart no paint on hammer. any thoughts thanks

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Stack

June 4, 2011, 10:41 PM

I had a similar problem when I assembled a Plumb Crazy lower matched to a DSA upper. I pulled the bolt apart and found the firing pin was floating in some very heavy oil. Kind of between grease and gun oil in consistency. I sprayed the bolt and carrier down with some aerosol CLP and re-assembled the BCG making sure the firing pin moved easily and voila!
Hope this helps ya.

runninmt

December 18, 2011, 11:08 PM

Olddog-newtrick, did you ever find out what the problem was? I have the exact same problem with the same set up. Seems like the hammer isn't even hitting the firing pin. I removed the bolt carrier group from the upper to take a closer look. Seems I can't even make the firing pin protrude from the front of the bolt while pushing it forward with my index finger. Maybe broken firing pin?

7.62 Nato

December 18, 2011, 11:23 PM

Could it possibly require a different hammer like some of the 9mm uppers? Does the lower have a standard/milspec hammer?

wally

December 19, 2011, 02:12 PM

It the Chiappa upper is anything like my 1911-22, there is your problem.

Rail Driver

December 19, 2011, 02:14 PM

The plum crazy lowers have a hammer that is wider than a standard hammer. Swap out the LPK with a standard LPK and it will fire. You can also file down the sides of the plastic hammer so it fits in the slot and hits the firing pin. This is a well known and common issue. Also PCF sells a replacement hammer that will work with the dedicated .22LR uppers.

68wj

December 19, 2011, 02:51 PM

The plum crazy lowers have a hammer that is wider than a standard hammer. Swap out the LPK with a standard LPK and it will fire. You can also file down the sides of the plastic hammer so it fits in the slot and hits the firing pin. This is a well known and common issue. Also PCF sells a replacement hammer that will work with the dedicated .22LR uppers.
That's the word.

Narrow hammer available here: http://www.joeboboutfitters.com/PlumCrazy_Blow_Back_Hammer_PC_BlowBack_p/pc-blowback.htm
A Plum Crazy blow back hammer replaces the standard Plum Crazy hammer. The blow back hammer is has been designed to be slightly narrower, resulting in better compatibility with dedicated AR-15 .22LR and 9mm uppers.

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